Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$204.78	8.760%	$222.7187	$222.72	$222.70	$222.70
Purchase #2	$231.81	5.151%	$243.7505	$243.75	$243.75	$243.80
Purchase #3	$85.38	8.413%	$92.563	$92.56	$92.55	$92.60
Purchase #4	$97.35	4.175%	$101.4144	$101.41	$101.40	$101.40
Purchase #5	$221.55	13.513%	$251.4881	$251.49	$251.50	$251.50
Purchase #6	$78.99	13.558%	$89.6995	$89.70	$89.70	$89.70
Purchase #7	$26.53	11.414%	$29.5581	$29.56	$29.55	$29.60
7 purchase totals =	$946.39		$1,031.1923	$1,031.19	$1,031.15	$1,031.30